The casting for 'The Big Bang Theory' went through a few changes early on. In fact, initially, Kaley Cuoco's Penny character did not exist. The role was a completely different one, known as Katie, who didn't exactly play nice with others. All the changes truly worked to perfection, as the show turned into an iconic sitcom, lasting 12 seasons and running for over a decade. Things couldn't have been very different. Heck, Johnny Galecki could've potentially been cast as Sheldon, had he not changed his mind on which role he wanted. Galecki discussed his decision with Variety, "It was a very selfish request on my part. I hadn't been able to traverse those stories of the heart. I've often been cast as the best friend or the gay assistant of whatever character got to explore those relationships. I said I'd rather play this guy, who seems to have a future of romantic triumphs and difficulties."
It all worked out for the better, however, during the casting process, Sheldon aka Jim Parsons felt a little uncomfortable. While working his lines alongside Johnny Galecki, it was a weird type of first for Parsons, as he explained with EW.
It was a weird type of first for Jim Parsons. According to his comments alongside EW, he had never auditioned alongside someone he had seen work before. Jim was familiar with Galecki's work from his time on 'Roseanne', "I already knew who Johnny was from Roseanne. That was weird because I don't think I've ever auditioned alongside someone I had seen act before. I read with other people, but it was very clear that no one else was making the part their own more than Johnny did. He knew what he was doing and was doing it in a strong way. I didn't feel like he needed my help. I didn't feel like he was bleeding into my work. He was his own distinct thing."
Turns out, everyone had their own unique audition experiences and that includes Kaley Cuoco. Kaley recalls meeting Jim Parsons in the waiting room, the two shared a nice conversation, "At the audition, I saw Jim sitting there by himself, and we were the only two there. He was very quiet and had a BlackBerry in his hand, playing with it. He looks at me and said, "You don't know how to work this thing, do you? I just got it." He was very cute how he said it. I thought he could totally play Sheldon. Charming and innocent."
Everything worked the way it should have. We really can't imagine anyone else in the role of Sheldon and we can say the same for Leonard. Despite a couple of hiccups, everything worked out for the better.